1. Field of the Invention
This invention relates to a method of and a system for drawing a torsion coil from one position to another.
2. Description of the Prior Art
A torsion spring comprising a coil portion and a pair of leg portions extending from opposite end of the coil portion is incorporated in various products such as a videotape cassette. When incorporating the torsion spring into the products by an automated system, the torsion spring must be held in a predetermined attitude which is determined by the structure of the portion into which the torsion spring is incorporated.
Conventionally, a torsion spring which has been fed to a predetermined position is once drawn to a waiting position while kept in the attitude in which it has been held in the predetermined position, and the attitude of the torsion spring is changed while it is transferred to a predetermined position in the product.
For example, a torsion spring for a certain type of videotape cassette is incorporated into the cassette in the following procedure. That is, as shown in FIG. 5, a feed device 100 feeds a torsion spring 2 to a first waiting position where the torsion spring 2 abuts against a stopper 102 which is spring-urged downward. A drawing mechanism 108 has a pair of drawing chucks 106 each having a pin 104 as shown in FIG. 6. The drawing chucks 106 are moved toward each other as shown by arrows A and inserted into the coil portion 4 of the torsion spring 2. Then the chucks 106 are moved in the direction of arrow B in FIG. 5 to bring the torsion spring 2 to a second waiting position shown by broken line in FIG. 5. Then a transfer chuck 112 of a transfer mechanism 110 pinches the coil portion 4 and lifts upward the torsion spring 2, and then the transfer chuck 112 is rotated in the direction of arrow C by a predetermined angle, thereby holding the torsion spring 2 in a predetermined attitude in which it is to be incorporated into the cassette as shown in FIG. 7.
When the torsion spring 2 is fed to the first waiting position by the feeding device 100, the coil portion 4 of the torsion spring 2 is slid along the top surface of a linear feeder 114 with leg portions 6A and 6B suspended downward from the top surface on opposite sides thereof. Further, the drawing mechanism 108 draws the torsion spring 2 with the leg portions 6A and 6B suspended downward from the drawing chucks 106.
In the conventional system, the attitude of the torsion spring 2 is changed by rotation of the transfer chuck 112. Accordingly, the transfer mechanism 110 must be provided with a mechanism for rotating the transfer chuck 112, which complicates the structure of the transfer mechanism 110 and adds to the weight of the same, thereby preventing the torsion spring 2 from being incorporated at high speed.